1) Compare the population of the country with the number of registrations (as a rough guide to potential growth)
2) Forget about 'vanity' extensions (except for .tv (if that's counted as a vanity))
3) Base purchasing decisions on estimated/potential traffic above all other factors
4) Consider markets where rule/regulation changes might lead to new opportunities (eg in Australia relaxing the prohibition on sales this year)
5) Make sure you are confident in the local language.
6) If not, English domains may still do well but be much more selective & work out the level of English speaking for that particular market
7) For new landrush releases, get in quick & don't be afraid to take a punt
8) For landrushes that involve auctions, be very wary as initial hype might mean to pay too much
9) Be careful with hacks using cc-TLDs
10) Remember growth in cc-TLDs across the board is eclipsing the CNO trio and carefully selective markets are blitzing the tradtional g-TLDs
There's my 10 - might be struggling for 150 specific tips but there you go!